Field of the Invention
The present invention generally relates to integrated circuits, and, more specifically, to an approach for clock frequency modulation of a fixed frequency clock source.
Description of the Related Art
A clock signal of a computer is a particular type of signal that oscillates between a high state and a low state and is utilized like a metronome to coordinate actions of various circuits within the computer. A clock generator within the computer generates the clock signal. Although there are more complex arrangements, a common clock signal is in the form of a square wave with a 50% duty cycle (i.e., percent of time that a device spends in an active state as a fraction of the total time under consideration), usually with a fixed, constant frequency. Circuits using the clock signal for synchronization may become active at either the rising edge, falling edge, or, in the case of double data rate, both at the rising edge and at the falling edge of the clock cycle.
In operation, devices, such as processing units, within the computer may require slightly different clock frequencies than the other devices within the computer that also require clock signals. One approach to meeting the different clock signal demands is to provide a dedicated clock for each device (e.g., each processing unit or other device) that requires a clock. For example, an integrated circuit may be configured with a different phase-locked loop (PLL) for each device that requires a different clock frequency, even if the required frequencies for the devices are only slightly different. For example, if the required clock frequency for one processing unit is 100.0 MHz while the required clock frequency for another processing unit is slightly different at 100.5 MHz, those two processing units typically require separate PLLs. That way, each device can operate at the required frequency for that device. Unfortunately, having numerous dedicated clocks (e.g., PLLs) tends to occupy a relatively large amount of space on a semiconductor circuit. Thus, such an approach is typically undesirable.
As the foregoing illustrates, what is needed in the art is a more optimized approach to providing clock signals to the different devices within a computer.